Interfacial friction enabling ≤ 20 μm thin free-standing lithium strips for lithium metal batteries

A practical high-specific-energy Li metal battery requires thin (≤20 μm) and free-standing Li metal anodes, but the low melting point and strong diffusion creep of lithium metal impede their scalable processing towards thin-thickness and free-standing architecture. In this paper, thin (5 to 50 μm) and free-standing lithium strips were achieved by mechanical rolling, which is determined by the in situ tribochemical reaction between lithium and zinc dialkyldithiophosphate (ZDDP). A friction-induced organic/inorganic hybrid interface (~450 nm) was formed on Li with an ultra-high hardness (0.84 GPa) and Young’s modulus (25.90 GPa), which not only enables the scalable process mechanics of thin lithium strips but also facilitates dendrite-free lithium metal anodes by inhibiting dendrite growth. The rolled lithium anode exhibits a prolonged cycle lifespan and high-rate cycle stability (in excess of more than 1700 cycles even at 18.0 mA cm−2 and 1.5 mA cm−2 at 25 °C). Meanwhile, the LiFePO4 (with single-sided load 10 mg/cm2) ||Li@ZDDP full cell can last over 350 cycles with a high-capacity retention of 82% after the formation cycles at 5 C (1 C = 170 mA/g) and 25 °C. This work provides a scalable approach concerning tribology design for producing practical thin free-standing lithium metal anodes.


Figure S1 .
Figure S1.Schematic diagram of the rolling process for different thicknesses of lithium strips.

Figure S7 .
Figure S7.(a, b) Fitting results of k 3 -weighted Zn K-edge EXAFS spectrum of Li@ZDDP plotted in R-space and k-space, respectively; (c, d) Fitting results of k 3weighted Zn K-edge EXAFS spectrum of Cycled Li@ZDDP plotted in R-space and kspace, respectively; (e, f) Fitting results of k 3 -weighted Zn K-edge EXAFS spectrum of ZDDP plotted in R-space and k-space, respectively.

Figure S8 .
Figure S8.Optical photos of lithium strips (rolling to 40 μm) during actual processing.(a) No ZDDP was used for rolling (b) Rolling by using ZDDP

Figure S11 .
Figure S11.The voltage-time profiles of symmetrical cells with Li and Li@ZDDP at various current densities: (a) 0.5 mA cm -2 and 0.5 mA h cm -2 , (b) 1.0 mA cm -2 and 1.0 mA h cm -2 .

Figure S14 .
Figure S14.Morphology image of different capacity of the first Li stripping at 1.5 mA cm -2 .

Figure S15 .
Figure S15.The EDS image of 2.0 mA h Li stripping at 1.5 mA cm -2 .

Figure S16 .
Figure S16.Morphology image of different capacity of the first Li plating after stripping at 1.5 mA cm -2 .

Figure S17 .
Figure S17.In situ Raman spectra of electrolyte near anode-electrolyte interface during Li@ZDDP (a, d) and Li plating (b, e) with 1.0 M LiTFSI in DME:DOL=1:1 Vol% at the plating current density of 3 mA cm -2 .(c) Initial Raman spectra of Li and Li@ZDDP near anode-electrolyte interface.

Figure S18 .
Figure S18.(a) Atomic structure and adsorption energy among Li+ and the nano bifunctional film (above), ester-based SEI (bottom left) and ether-based SEI (bottom right).(b-f) The calculated electrostatic potential (ESP).

Figure S20 .
Figure S20.The voltage-time profiles of symmetrical cells with Li, Li@MO and

Table S2
EIS curves fitting parameters.S , Ohmic Impedance; R SEI , Li + transfer resistance; R CT, charge transfer resistance.The error bars were obtained from running the ZVIEW program with the EIS fitting.Prioritize to control of the error-R SEI in fitting analysis. R